Question

Trignometric identites..

Answer 1

tan(θ) = sin(θ)/cos(θ)

Half Angle Identities

Note that "±" means it may be either one, depending on the value of θ/2

sin a/2

cos a/2

tan a/2

cot a/2

Explanation:

Answer 2

TOA CAH SOH
Pythagoras Theorem
Sine rule
Cosine Rule